Known in the past has been an electrochemical reactor provided with an ion conductive solid electrolyte and an anode layer and a cathode layer provided on a surface of the solid electrolyte (for example, PTLs 1, 2). In such an electrochemical reactor, by applying current through the anode layer and the cathode layer, it is possible to remove the NOX in the exhaust gas on the cathode layer.
As such an electrochemical reactor, there is known one provided with a honeycomb member including a solid electrolyte and providing each cell of the honeycomb member with anode layers or cathode layers (for example, PTL 1). In particular, in the electrochemical reactor described in PTL 1, one cell among two adjoining cells is provided with anode layers while the other cell is provided with cathode layers.